Pump



April 1957 A. DOLAN r-rrm. 2,787,963

PUMP

Filed May 5, 1953 INVENTORS.

Z6 35012113 g golarz/ pig/d I race ungzgren,

PUMP

Louis A. Dolan and Bruce H. Lundgren, Rockford, lll.,

assignors to Sundstrand Machine Tool (30., a corporation of Illinois Application May 5, 1953, Serial No. 353,038

3 Claims. (Cl. 103-126) This invention relates to a pump and more particularly to a gear type fluid pump.

It is the general object of this invention to produce a new and improved pump of the character described.

It is a more specific object of the invention to produce a gear type fluid pump in which means are provided for assuring proper sealing engagement between the side faces of the gear and the end faces in contact therewith so as to maintain a high volumetric efiiciency of the pump.

A further object of the invention is to produce a pump of the type described in the preceding paragraphs which includes a rotatable end plate positioned to contact the side face of the gear together with means for urging the plate into contact with the side face so as to provide a seal therebetween while simultaneously reducing the wear on the side face and the plate.

Still another object of the invention is to produce a gear pump of the crescent type, that is to produce a gear pump which includes an internally toothed ring gear rotatably positioned in a pumping chamber and meshing with the teeth of a pinion gear smaller in diameter than the ring gear so as to leave an arcuate space therebetween, with said space being occupied by a crescent shaped member and in which the side faces of the gears and crescent engage one face of an end plate rotatably mounted in the pumping chamber together with means for applying pressure to the opposite face of the end plate to urge the same into sealing engagement with said side faces.

A corollary feature of the pump described in the preceding paragraph may include a construction wherein the crescent member has a thickness slightly less than the thickness of the gears, thus to relieve the wear on the rotating end plate at the location of the crescent member.

Other and further objects and advantages of the invention will be readily apparent from the following description and drawings, in which:

Fig. 1 is a longitudinal, sectional view of a gear pump embodying the invention;

Fig. 2 is a transverse section taken along line 2-2 of Fig. 1; and- Fig. 3 is a sectional view showing the ring and pinion gears, crescent and rotatable end plate in a slightly modified form of construction.

While this invention is susceptible of embodiments in many different forms, there are shown in the drawings and will herein be described in detail several embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawings, the pump of the present invention includes a casing generally indicated at States Patent G ice comprising a body portion 11 and an end cap 12 secured to the body portion by a plurality of bolts 13. The body portion is provided with an inlet 14 and an outlet 15 and the end cap 12 is formed as to provide a substantially cylindrical pumping chamber 16. The pumping chamber communicates with the inlet 14 through a passage 17 formed in the body portion and with the outlet 15 through a second passage 18 also formed in the body portion.

The pumping chamber 16 is provided with two substantially parallel end faces 19 and 20 and the body portion 11 rotatably supports a pump drive shaft 22.

Fixed to the inner end of the drive shaft is a pinion gear 23 having external teeth meshing with the internal teeth formed on a ring gear 24. The ring gear has an external diameter substantially equal to the diameter of the pumping chamber 16 and an internal diameter larger than the external diameter of the pinion to provide therebetween an arcuate space occupied by a crescent shaped member 25 fixed to the end face 19.

The gears and the crescent member may be of substantially equal thickness so as to position the side face 26 of the ring gear, the side face 27 of the pinion and the side face 28 of the crescent substantially in a common plane.

Engaging the side faces 2643 and located in the pumping chamber 16 is a rotatable end plate 30. The end plate 30 is circular in shape and has a diameter substantially equal to the diameter of the pumping chamber. One face 31 of the end plate engages the side faces 2628 of the gears and crescent while the opposite face 32 of the end plate is adjacent to but spaced from the end face 20 in the pumping chamber so as to provide therebetween a pressure chamber 33.

As previously noted, the end plate 30 is free to rotate in the pumping chamber and means are provided for biasing the end plate toward the side faces of the gears and crescent so as to provide at least a partial seal during start-up of the pump. To this end the face 32 of the end plate is provided with a recess 35 while the end cap 12 is provided with a generally cylindrical recess 36, the axis of which is coincident with the axis of the pumping chamber. Positioned in the recess 36 is a compression spring 37 which bears against a ball 38 seated in the recess 35.

As previously noted, the spring means are provided for preloading the pump during start-up, and other means are provided for pressurizing the back face 32 of the end plate when the pump is in operation more firmly to urge the end plate into sealing engagement with the side faces of the gears and crescent.

To this end the body member 11 is provided with a fluid passage 40 opening at one end to the outlet passage 18 and communicating at its other end with a passage 41 in the end cap. The passage 41 communicates with a second passage 42 in the end cap which opens into the pressure chamber 33. Thus, during operation of the pump fluid under pressure from the outlet is directed into the pressure chamber 33 firmly to press the end plate 39 against the side faces of the gear and crescent.

Because of the fact that the end plate 30 is free to rotate in the pumping chamber with rotation of the gears, wear on the engaging side faces of the gears and crescent and the face 31 of the end plate is reduced. Wear between the opposite side faces of the gears and the end face 19 of the pumping chamber is taken up by the end plate 30 and thus there is provided a gear pump which will retain its pumping efficiency over a relatively long period.

As previously noted, the crescent member 25 is fixed to the end face 19 and thus relative rotation occurs, in

the embodiments illustrated, between. the side face 28 of the crescent member and the end plate 30. As wear in the contacting areas between the surfaces just mentioned may exceed the wear between the face 31 of the end plate and the rotating gears, it may be advisable to relieve the surface 28 of the crescent member so as to reduce such wear. Such a form of construction is illustrated in Fig. 3 wherein the crescent member a is again positioned between the pinion 23a and the ring gear 24a and is pinned to' the side face 19a. A pressure plate is provided which engages the side faces 26a and 27a of the ring gear and crescent, respectively, but the side face 28a of. the crescent shaped member has been slightly relieved to provide a small space between such side face and the mating face of the end plate. Thus, the thickness of the crescent shaped member is slightly less than the thickness of the gears and the space thereby provided is, during operation of the pump, occupied by a film of oil. The slight leakage which may occur over the face 28a of the crescent member is negligible and the efiiciency of the pump is not grcatlyaffccted.

We claim:

1. A pump comprising: a casing having a generally cylindrical pumping chamber therein having spaced parallel end faces and having an inlet and an outlet, an internally toothed ring gear in the chamber and having a diameter substantially equal to the diameter of. the charm ber, a drive shaft rotatably mounted in the casing, a pinion gear in the chamber and fixed to the drive shaft, said pinion having external teeth meshing with the teeth of the ring gear and having a diameter substantially less than the diameter of the ring gear to provide an arcuate space therebetween, a crescent shaped member fixed in the chamber and positioned in said arcuate space with the opposite ends of said member being located adjacent the inlet and the outlet and with said gears being of substantially equal thickness to position the side faces thereof substantially in a common plane, a relatively inflexible circular end plate having a diameter substantially equal to said diameter of the ring gear mounted in the chamber for free rotation therein relative to the shaft, gears, member, and chamber, said end plate having one face engaging the side faces of the gears and having its opposite face adjacentbut spaced from the adjacent end face of the chamber to provide therebetween a pressure chamber, spring means biasing the pressure plate toward said gears, and a fluid passage in the casing connecting said pressure chamber to said outlet to pressurize said oppositeface of the plate to urge the plate into sealing engagement with the side faces of the gears and said crescent member.

2. A pump comprising: a casing having a generally cylindrical pumping chamber therein having spaced parallel end faces and having an inlet and an outlet, an internally toothed ring gear in. the chamber and having a diameter substantially equal to the diameter of the chamber, a drive shaft rotatably mounted in the casing, a pin ion gear in the chamber and fixed to the drive shaft, said pinion having external teeth meshing with the teeth of the ring gear and having a diameter substantially less than the diameter of the ring gear to provide an arcuate space therebetween, a crescent shaped member fixed in the chamber and positioned in said arcuate space with the opposite ends of said member being located adjacent the inlet and outlet, said gears being of equal thickness slightly greater than the thickness of the crescent shaped member, a relatively inflexible end plate mounted in the chamber for free rotation therein relative to the shaft, gears, crescent, and chamber, said end plate having one face engaging the side faces of the gears and slightly spaced from the side face of the crescent member and having its opposite face adjacent but spaced from the adjacent end face of the chamber to provide thercbetween a pressure chamber, spring means biasing the pressure plate toward said gears, and a fluid passage in the casing connecting said pressure chamber to said outlet to pressurize said opposite face of the plate to urge the plate into sealing engagement with the side faces of the gears.

3. A pump comprising: a casing having a generally cylindrical pumping chamber therein having spaced parallel end faces and having an inlet and an outlet, an internally toothed ring gear in the chamber and having a diameter substantially equal to the diameter of the chamber, a drive shaft rotatably mounted in the casing, a pinion gear in the chamber and fixed to the drive shaft, said pinion having external teeth meshing with the teeth of the ring gear and having a diameter substantially less than the diameter of the ring gear to provide an arcuatc space therebetween, a crescent shaped member fixed in the chamber and positioned in said arcuate space with the opposite ends of said member being located adjacent the inlet and the outlet and with said gears and said crescent member being of substantially equal thickness to position the side faces thereof substantially in a common plane, a relatively inflexible circular end plate having a diameter substantially equal to said diameter of the ring gear mounted in the chamber for free rotation therein relative to the shaft, gears, member, and chamber, said end plate having one face engaging the side faces of the gears and havin its opposite face adjacent but spaced from the adjacent end face of the chamber to provide therebetween a pressure chamber, a cylindrical recess in the last mentioned end face coincident with the center of the chamber, a ball seated in a recess at the center of said opposite face of the plate, a spring in said cylindrical recess and bearing against the ball to bias the plate toward said gears, and a fluid passage in the casing connecting said pressure chamber to said outlet to pressurize said opposite face of the plate to urge the plate into sealing engagement with the side faces of the gears and said crescent member.

References Cited in the file of this patent UNITED STATES PATENTS 1,501,051 Hill July 15, 1924 1,793,577 Wilsey Feb. 24, 1931 2,146,037 Wahlmark Feb. 7, 1939 2,151,482 Neeson Mar. 21, 1939 2,383,153 Parsons Aug. 21, 1945 2,434,135 Witchger Jan. 6, 1948 2,490,115 Clarke Dec. 6, 1949 2,490,391 Wentling Dec. 6, 1949 2,650,544 Parsons Sept. 1, 1953 

